Abstract Although the majority of breast cancer patients choose some form of breast mound reconstruction after mastectomy, a large group of women - 27% of early-stage patients in the United States (Jagsi et. al., J Clin Oncol. 2014 Mar 20; 32(9): 919-926)) - affirmatively choose to “go flat.” The language is evolving but these patients will often request a smooth, breastless chest contour, or “flat closure.” The problem is that there is a near complete deficit in the existing body of scientific literature addressing these patients’ satisfaction with the surgery’s cosmetic result. As a result, patients face significant uncertainty in the quality of their surgical management and outcome, and report struggling to advocate for and protect their reconstructive choice. To address this deficit, we conducted two ad-hoc surveys to gather preliminary data on patient experience with flat closure cosmesis. The surveys were prepared and organized into Google Forms for online distribution to several private social media support groups for women going flat after mastectomy. Participant identities were anonymized via participant code. The pilot analysis included 142 (of 147 after necessary exclusions) responses collected from July 1, 2018 to February 1, 2019, and the second survey included 175 (of 183) responses from April 26, 2019 to June 09, 2019. Mean elapsed time between surgery and survey was 2.7 years (range = 3 months to 30 years) for the pilot and 3.2 years (range = 0 to 24 years) for the second survey. In the pilot, the majority of respondents (75%) were satisfied (rating = 6-10) with their initial result; this approaches the 64-69% satisfaction at two years that has been established for patients who have undergone breast mound reconstruction (Santosa et. al., JAMA Surg. 2018 Oct; 153(10): 891-899). No change in satisfaction from surgery to present day was observed for those patients who did not have revision surgery, meaning additional surgery to improve the post-mastectomy chest contour. However, for patients who did pursue revision, we saw drastically improved satisfaction, from a mean of 2/10 before, to a mean of 9/10 after. Overall, the incidence of intentional flat denial (IFD) - which we define as leaving the patient with excess tissue to facilitate future reconstruction against her consent - was 5% (n = 8). Among those who reported dissatisfaction with their cosmetic result (rating ≤ 4), the IFD incidence was close to one in five (19%). The second survey found a similar overall IFD incidence of 4% (n = 7). The incidence of negligent flat denial (NFD) - which we defined as a very poor “expectation match” (divergence of actual vs. expected cosmetic result, rating ≤ 2/10) together with the reported presence of excess tissue - was 7% (n = 13). Patients reported experiencing moderate to severe preoperative pushback from their surgeon about their reconstructive choice (rating ≥ 6/10) at rates of 71% (IFD), 46% (NFD), and 23% (no flat denial). Overall, 81% of patients reported that minimizing their surgical recovery period was a very important decision factor in going flat (rating ≥ 8/10). The incidence of revision surgery - which extends the surgical recovery period - was 26% overall, but was much higher for those patients subjected to IFD (43%) and NFD (54%). These data suggest that implementation of uniform surgical management and improved respect for patient consent in this population could result in significantly improved patient experience and satisfaction. Specifically, the need for surgical revision could be reduced to better align these patients’ experience with their stated priorities. We hope that these results will encourage the commission of larger scale studies using validated tools, translating to an improved, evidence-based standard of care for women who choose to go flat after mastectomy. Citation Format: Kimberly B Bowles. Flat closure after mastectomy: Are your patients satisfied with the results? [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-11-23.